U.S. patent number 5,835,285 [Application Number 08/882,802] was granted by the patent office on 1998-11-10 for projection optical system and exposure apparatus using the same.
This patent grant is currently assigned to Nikon Corporation. Invention is credited to Kazumasa Endo, Misako Kobayashi, Hitoshi Matsuzawa, Yutaka Suenaga.
United States Patent |
5,835,285 |
Matsuzawa , et al. |
November 10, 1998 |
Projection optical system and exposure apparatus using the same
Abstract
The present invention relates to an exposure apparatus using a
projection optical system to realize a small size and the
bitelecentricity as securing a wide exposure area and a large
numerical aperture and to realize extremely good correction for
aberrations, particularly for distortion. The projection optical
system comprises a first lens group G.sub.1 with a positive
refracting power, a second lens group G.sub.2 with a negative
refracting power, a third lens group G.sub.3 with a positive
refracting power, a fourth lens group G.sub.4 with a negative
refracting power, a fifth lens group G.sub.5 with a positive
refracting power, and a sixth lens group G.sub.6 with a positive
refracting power in order from the side of the first object R,
wherein the second lens group G.sub.2 comprises a front lens
L.sub.2F with a negative refracting power, a rear lens L.sub.2R of
a negative meniscus shape, and an intermediate lens group G.sub.2M
disposed between the front lens and the rear lens, and wherein the
intermediate lens group G.sub.2M has a first lens L.sub.M1 with a
positive refracting power, a second lens L.sub.M2 with a negative
refracting power, and a third lens L.sub.M3 with a negative
refracting power in order from the side of the first object R. The
system is arranged to satisfy within suitable ranges of focal
lengths for the first to sixth lens groups G.sub.1 -G.sub.6, based
on the above arrangement.
Inventors: |
Matsuzawa; Hitoshi
(Setagaya-ku, JP), Kobayashi; Misako (Setagaya-ku,
JP), Endo; Kazumasa (Kawasaki, JP),
Suenaga; Yutaka (Yokohama, JP) |
Assignee: |
Nikon Corporation
(JP)
|
Family
ID: |
11485769 |
Appl.
No.: |
08/882,802 |
Filed: |
June 30, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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516903 |
Aug 18, 1995 |
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Foreign Application Priority Data
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Jan 6, 1995 [JP] |
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7-000872 |
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Current U.S.
Class: |
359/754; 359/649;
430/311 |
Current CPC
Class: |
G02B
13/24 (20130101); G03F 7/70241 (20130101); G02B
9/62 (20130101); G02B 13/22 (20130101) |
Current International
Class: |
G03F
7/20 (20060101); G02B 13/22 (20060101); G02B
13/24 (20060101); G02B 9/62 (20060101); G02B
9/00 (20060101); G02B 009/64 (); G03C 005/00 () |
Field of
Search: |
;359/754,755,756,649
;430/311 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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May 1996 |
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EP |
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0 717 299 A |
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Jun 1996 |
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EP |
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47-35017 |
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Sep 1972 |
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JP |
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55-12902 |
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Jan 1980 |
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JP |
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63-118115 |
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May 1988 |
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JP |
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4-157412 |
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May 1992 |
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JP |
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6-313845 |
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Nov 1994 |
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JP |
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WO 93/04391 |
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Mar 1993 |
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WO |
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Other References
J Braat, "Quality of Microlithographic Projection Lenses", pp.
22-30, Proceedings of SPIE vol. 811, Optical Microlithographic
Technology for Integrated Circuit Fabrication and Inspection
(1987). .
Patent Abstracts of Japan, vol. 7, No. 73 (P-186) and JP-580 041
112, Jan. 11, 1983. .
Patent Abstracts of Japan, vol. 12, No. 366 (P-765) and JP-631 118
115, May 23, 1988. .
Patent Abstracts of Japan, vol. 17, no. 586 (P-1633) and JP-517
3065, Jul. 13, 1993..
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Primary Examiner: Sugarman; Scott J.
Attorney, Agent or Firm: Pennie & Edmonds LLP
Parent Case Text
This is a continuation of application Ser. No. 08/516,903, filed
Aug. 18, 1995, now abandoned.
Claims
What is claimed is:
1. A projection optical system provided between a first object and
a second object, for projecting an image of a first object onto a
second object, said projection optical system comprising a first
lens group with a positive refracting power, a second lens group
with a negative refracting power, a third lens group with a
positive refracting power, a fourth lens group with a negative
refracting power, a fifth lens group with a positive refracting
power, and a sixth lens group with a positive refracting power in
order from the side of said first object,
wherein said second lens group comprises a front lens with a
negative refracting power disposed as closest to said first object
and shaped with a concave surface to said second object, a rear
lens of a negative meniscus shape disposed as closest to said
second object and shaped with a concave surface to said first
object, and an intermediate lens group disposed between said front
lens and said rear lens, said intermediate lens group having a
first lens with a positive refracting power, a second lens with a
negative refracting power, and a third lens with a negative
refracting power in order from the side of said first object,
and
wherein when f.sub.1 is a focal length of said first lens group,
f.sub.2 is a focal length of said second lens group, f.sub.3 is a
focal length of said third lens group, f.sub.4 is a focal length of
said fourth lens group, f.sub.5 is a focal length of said fifth
lens group, f.sub.6 is a focal length of said sixth lens group, and
L is a distance from said first object to said second object, the
following conditions are satisfied:
2. A projection optical system according to claim 1, wherein when I
is an axial distance from said first object to a first-object-side
focal point of said entire projection optical system and L is the
distance from said first object to said second object, the
following condition is satisfied:
3. A projection optical system according to claim 1, wherein said
fourth lens group comprises:
a front lens group disposed as closest to the first object, said
front lens group having two negative meniscus lenses each shaped
with a concave surface to said second object;
a rear lens group disposed as closest to the second object, said
rear lens group having a negative lens with a concave surface to
said first object; and
an intermediate lens group disposed between said front lens group
in said fourth lens group and said rear lens group in said fourth
lens group, said intermediate lens group having first and second
negative lenses in order from the side of said first object,
and
wherein when f.sub.4A is a focal length of said first negative lens
in said fourth lens group and f.sub.4B is a focal length of said
second negative lens in said fourth lens group, the following
condition is satisfied:
4. A projection optical system according to claim 1, wherein when
r.sub.2Ff is a radius of curvature of a first-object-side surface
of said front lens and r.sub.2Fr is a radius of curvature of a
second-object-side surface of said front lens, the front lens in
said second lens group satisfies the following condition:
5. A projection optical system according to claim 1, wherein said
fourth lens group has:
a front lens group having a negative lens disposed as closest to
said first object and shaped with a concave surface to said second
object;
a rear lens group having a negative lens disposed as closest to the
second object and shaped with a concave surface to said first
object; and
an intermediate lens group having a negative lens and a positive
lens with a convex surface adjacent to a concave surface of said
negative lens is disposed between said front lens group in said
fourth lens group and said rear lens group in said fourth lens
group, and
wherein when r.sub.4N is a radius of curvature of said concave
surface of the negative lens in said intermediate lens group and
r.sub.4P is a radius of curvature of said convex surface of the
positive lens in said intermediate lens group, the following
condition is satisfied:
provided that when L is the distance from said first object to said
second object, said concave surface of said negative lens in said
intermediate lens group or said convex surface of said positive
lens in said intermediate lens group satisfies at least one of the
following conditions :
6. A projection optical system according to claim 1, wherein when
f.sub.22 is a focal length of the second lens with the negative
refracting power in said second lens group and f.sub.23 is a focal
length of the third lens with the negative refracting power in said
second lens group, the following condition is satisfied:
7. A projection optical system according to claim 1, wherein said
fifth lens group has a negative meniscus lens, and a positive lens
disposed as adjacent to a concave surface of said negative meniscus
lens and having a convex surface opposed to the concave surface of
said negative meniscus lens, and
wherein when r.sub.5n is a radius of curvature of the concave
surface of said negative meniscus lens in said fifth lens group and
r.sub.5P is a radius of curvature of the convex surface, opposed to
the concave surface of the negative meniscus lens, of the positive
lens disposed as adjacent to the concave surface of said negative
meniscus lens in said fifth lens group, the following condition is
satisfied:
8. A projection optical system according to claim 7, wherein said
negative meniscus lens and said positive lens adjacent to the
concave surface of said negative meniscus lens are disposed between
at least one positive lens in said fifth lens group and at least
one positive lens in said fifth lens group.
9. A projection optical system according to claim 1, wherein said
fifth lens group has a negative lens disposed as closest to the
second object and shaped with a concave surface to the second
object and the sixth lens group has a lens disposed as closest to
the first object and shaped with a convex surface to the first
object, and
wherein when r.sub.5R is a radius of curvature of a
second-object-side surface of the negative lens disposed as closest
to the second object in said fifth lens group and r.sub.6F is a
radius of curvature of a first-object-side surface of the lens
disposed as closest to the first object in said sixth lens group,
the following condition is satisfied:
10. A projection optical system according to claim 1, wherein when
d.sub.56 is a lens group separation between said fifth lens group
and said sixth lens group and L is the distance from said first
object to said second object, the following condition is
satisfied:
11. A projection optical system according to claim 1, wherein when
r.sub.6F is a radius of curvature of a lens surface closest to the
first object in said sixth lens group and d.sub.6 is an axial
distance from the lens surface closest to the first object in said
sixth lens group to the second object, the following condition is
satisfied:
12. A projection optical system according to claim 1, wherein said
fifth lens group has a negative lens disposed as closest to the
second object and shaped with a concave surface to the second
object, and wherein when r.sub.5F is a radius of curvature of a
first-object-side surface of the negative lens disposed as closest
to the second object in said fifth lens group and r.sub.5R is a
radius of curvature of a second-object-side surface of the negative
lens disposed as closest to the second object in said fifth lens
group, the following condition is satisfied:
13. A projection optical system according to claim 1, wherein when
f.sub.2 is a focal length of the first lens with the positive
refracting power in the intermediate lens group in said second lens
group and L is the distance from said first object to said second
object, the following condition is satisfied:
14. A projection optical system according to claim 1, wherein when
f.sub.2F is a focal length of the front lens with the negative
refracting power disposed as closest to the first object in said
second lens group and shaped with the concave surface to said
second object and f.sub.2R is a focal length of the rear lens with
the negative refracting power disposed as closest to the second
object in said second lens group and shaped with the concave
surface to said first object, the following condition is
satisfied:
15. A projection optical system according to claim 1, wherein the
intermediate lens group in said second lens group has a negative
refracting power.
16. A projection optical system according to claim 1, wherein said
first lens group has at least two positive lenses, said third lens
group has at least three positive lenses, said fourth lens group
has at least three negative lenses, said fifth lens group has at
least five positive lenses and at least one negative lens, and said
sixth lens group has at least one positive lens.
17. A projection optical system according to claim 1, wherein said
sixth lens group comprises three or less lenses having at least one
lens surface satisfying the following condition:
where .phi.: a refractive power of said lens surface, and L: the
object-to-image distance from said first object to said second
object.
18. A projection optical system according to claim 1, wherein a
magnification of said projection optical system is 1/5.
19. A method for manufacturing integrated circuits, said method
including an exposure process of projecting an image of a pattern
on a mask onto a photosensitive substrate with an exposure light of
a predetermined wavelength, said exposure process comprising the
steps of;
supplying said exposure light;
introducing said exposure light to said mask;
making said exposure light passing through said mask incident on a
projection optical system according to claim 1; and
introducing said exposure light passing through said projection
optical system onto said photosensitive substrate.
20. A projection optical system according to claim 1, wherein said
fifth lens group comprises a negative lens placed as closet to the
second object and having a concave surface opposed to the second
object.
21. A projection optical system according to claim 20, wherein when
d.sub.56 is a lens group separation between said fifth lens group
and said sixth lens group and L is the distance from said first
object to said second object, the following condition is
satisfied:
22. A projection optical system according to claim 20, wherein when
r.sub.6F is a radius of curvature of a lens surface closest to the
first object in said sixth lens group and d.sub.6 is an axial
distance from the lens surface closest to the first object in said
sixth lens group to the second object, the following condition is
satisfied:
0.50<d.sub.6 /r.sub.6F <1.50.
23. A projection optical system according to claim 20, wherein said
sixth lens group comprises three or less lenses having at least one
lens surface satisfying the following condition:
where .phi.: a refractive power of said lens surface, and
L: the object-to-image distance from said first object to said
second object.
24. A projection optical system according to claim 16, wherein when
I is an axial distance from said first object to a
first-object-side focal point of said entire projection optical
system and L is the distance from said first object to said second
object, the following condition is satisfied:
25. A projection optical system according to claim 24, wherein said
fifth lens group has a negative meniscus lens, and a positive lens
disposed as adjacent to a concave surface of said negative meniscus
lens and having a convex surface opposed to the concave surface of
said negative meniscus lens, and
wherein when r.sub.5n is a radius of curvature of the concave
surface of said negative meniscus lens in said fifth lens group and
r.sub.5P is a radius of curvature of the convex surface, opposed to
the concave surface of the negative meniscus lens, of the positive
lens disposed as adjacent to the concave surface of said negative
meniscus lens in said fifth lens group, the following condition is
satisfied:
26. A projection optical system according to claim 25, wherein said
negative meniscus lens and said positive lens adjacent to the
concave surface of said negative meniscus lens are disposed between
at least one positive lens in said fifth lens group and at least
one positive lens in said fifth lens group.
27. A projection optical system according to claim 26, wherein said
fifth lens group comprises a negative lens placed as closest to the
second object and having a concave surface opposed to the second
object.
28. A projection optical system according to claim 27, wherein when
r.sub.6F is a radius of curvature of a lens surface closest to the
first object in said sixth lens group and d.sub.6 is an axial
distance from the lens surface closest to the first object in said
sixth lens group to the second object, the following condition is
satisfied:
29. A projection optical system according to claim 28, wherein when
f.sub.22 is a focal length of the second lens with the negative
refracting power in said second lens group and f.sub.23 is a focal
length of the third lens with the negative refracting power in said
second lens group, the following condition is satisfied:
30. A projection optical system according to claim 29, wherein when
f.sub.21 is a focal length of the first lens with the positive
refracting power in the intermediate lens group in said second lens
group and L is the distance from said first object to said second
object, the following condition is satisfied:
31. A method for manufacturing integrated circuits, said method
including an exposure process of projecting an image of a pattern
on a mask onto a photosensitive substrate with an exposure light of
a predetermined wavelength, said exposure process comprising the
steps of:
supplying said exposure light;
introducing said exposure light to said mask;
making said exposure light passing through said mask incident on a
projection optical system according to claim 30; and
introducing said exposure light passing through said projection
optical system onto said photosensitive substrate.
32. A method for manufacturing integrated circuits, said method
including an exposure process of projecting an image of a pattern
on a mask onto a photosensitive substrate with an exposure light of
a predetermined wavelength, said exposure process comprising the
steps of:
supplying said exposure light;
introducing said exposure light to said mask;
making said exposure light passing through said mask incident on a
projection optical system according to claim 28; and
introducing said exposure light passing through said projection
optical system onto said photosensitive substrate.
33. A projection optical system according to claim 24, wherein said
fourth lens group comprises:
a front lens group disposed as closest to the first object, said
front lens group having two negative meniscus lenses each shaped
with a concave surface to said second object;
a rear lens group disposed as closest to the second object, said
rear lens group having a negative lens with a concave surface to
said first object; and
an intermediate lens group disposed between said front lens group
in said fourth lens group and said rear lens group in said fourth
lens group, said intermediate lens group having first and second
negative lenses in order from the side of said first object,
and
wherein when f.sub.4A is a focal length of said first negative lens
in said fourth lens group and f.sub.4B is a focal length of said
second negative lens in said fourth lens group, the following
condition is satisfied:
34. A projection optical system according to claim 24, wherein when
r.sub.Ff is a radius of curvature of a first-object-side surface of
said front lens and r.sub.Fr is a radius of curvature of a
second-object-side surface of said front lens, the front lens in
said second lens group satisfies the following condition:
35. A projection optical system according to claim 24, wherein said
fourth lens group has:
a front lens group having a negative lens disposed as closest to
said first object and shaped with a concave surface to said second
object;
a rear lens group having a negative lens disposed as closest to the
second object and shaped with a concave surface to said first
object; and
an intermediate lens group having a negative lens and a positive
lens with a convex surface adjacent to a concave surface of said
negative lens is disposed between said front lens group in said
fourth lens group and said rear lens group in said fourth lens
group, and
wherein when r.sub.4N is a radius of curvature of said concave
surface of the negative lens in said intermediate lens group and
r.sub.4P is a radius of curvature of said convex surface of the
positive lens in said intermediate lens group, the following
condition is satisfied:
provided that when L is the distance from said first object to said
second object, said concave surface of said negative lens in said
intermediate lens group or said convex surface of said positive
lens in said intermediate lens group satisfies at least one of the
following conditions :
36. A projection optical system according to claim 24, wherein said
fifth lens group comprises a negative lens placed as closest to the
second object and having a concave surface opposed to the second
object.
37. A projection optical system according to claim 36, wherein when
r.sub.6F is a radius of curvature of a lens surface closest to the
first object in said sixth lens group and d.sub.6 is an axial
distance from the lens surface closest to the first object in said
sixth lens group to the second object, the following condition is
satisfied:
38. A projection optical system according to claim 37, wherein when
f.sub.22 s a focal length of the second lens with the negative
refracting power in said second lens group and f.sub.23 is a focal
length of the third lens with the negative refracting power in said
second lens group, the following condition is satisfied:
39. A projection optical system according to claim 38, wherein when
f.sub.21 is a focal length of the first lens with the positive
refracting power in the intermediate lens group in said second lens
group and L is the distance from said first object to said second
object, the following condition is satisfied:
40. A method for manufacturing integrated circuits, said method
including an exposure process of projecting an image of a pattern
on a mask onto a photosensitive substrate with an exposure light of
a predetermined wavelength, said exposure process comprising the
steps of:
supplying said exposure light;
introducing said exposure light to said mask;
making said exposure light passing through said mask incident on a
projection optical system according to claim 39; and
introducing said exposure light passing through said projection
optical system onto said photosensitive substrate.
41. A projection optical system according to claim 24, wherein when
f.sub.22, is a focal length of the second lens with the negative
refracting power in said second lens group and f.sub.23 is a focal
length of the third lens with the negative refracting power in said
second lens group, the following condition is satisfied:
42. A projection optical system according to claim 41, wherein when
f.sub.21 is a focal length of the first lens with the positive
refracting power in the intermediate lens group in said second lens
group and L is the distance from said first object to said second
object, the following condition is satisfied:
43. A projection optical system according to claim 24, wherein when
f.sub.21 is a focal length of the first lens with the positive
refracting power in the intermediate lens group in said second lens
group and L is the distance from said first object to said second
object, the following condition is satisfied:
44. A method for manufacturing integrated circuits, said method
including an exposure process of projecting an image of a pattern
on a mask onto a photosensitive substrate with an exposure light of
a predetermined wavelength, said exposure process comprising the
steps of:
supplying said exposure light;
introducing said exposure light to said mask;
making said exposure light passing through said mask incident on a
projection optical system according to claim 24; and
introducing said exposure light passing through said projection
optical system onto said photosensitive substrate.
45. A projection optical system according to claim 16, wherein said
fifth lens group has a negative meniscus lens, and a positive lens
disposed as adjacent to a concave surface of said negative meniscus
lens and having a convex surface opposed to the concave surface of
said negative meniscus lens, and
wherein when r.sub.5n is a radius of curvature of the concave
surface of said negative meniscus lens in said fifth lens group and
r.sub.5P is a radius of curvature of the convex surface, opposed to
the concave surface of the negative meniscus lens, of the positive
lens disposed as adjacent to the concave surface of said negative
meniscus lens in said fifth lens group, the following condition is
satisfied:
46. A projection optical system according to claim 45, wherein said
negative meniscus lens and said positive lens adjacent to the
concave surface of said negative meniscus lens are disposed between
at least one positive lens in said fifth lens group and at least
one positive lens in said fifth lens group.
47. A method for manufacturing integrated circuits, said method
including an exposure process of projecting an image of a pattern
on a mask onto a photosensitive substrate with an exposure light of
a predetermined wavelength, said exposure process comprising the
steps of:
supplying said exposure light;
introducing said exposure light to said mask;
making said exposure light passing through said mask incident on a
projection optical system according to claim 46; and
introducing said exposure light passing through said projection
optical system onto said photosensitive substrate.
48. An exposure apparatus comprising:
a stage allowing a photosensitive substrate to be held on a main
surface thereof;
an illumination optical system for emitting exposure light of a
predetermined wavelength and transferring a predetermined pattern
of a mask onto said substrate; and
a projection optical system provided between said mask and said
substrate, said projection optical system including a first lens
group with a positive refracting power, a second lens group with a
negative refracting power, a third lens group with a positive
refracting power, a fourth lens group with a negative refracting
power, a fifth lens group with a positive refracting power, and a
sixth lens group with a positive refracting power in order from the
side of said mask,
wherein said second lens group comprises a front lens with a
negative refracting power disposed as closest to said first object
and shaped with a concave surface to said second object, a rear
lens of a negative meniscus shape disposed as closest to said
second object and shaped with a concave surface to said mask, and
an intermediate lens group disposed between said front lens and
said rear lens, said intermediate lens group having a first lens
with a positive refracting power, a second lens with a negative
refracting power, and a third lens with a negative refracting power
in order from the side of said mask, and
wherein when f.sub.1 is a focal length of said first lens group,
f.sub.2 is a focal length of said second lens group, f.sub.3 is a
focal length of said third lens group, f.sub.4 is a focal length of
said fourth lens group, f.sub.5 is a focal length of said fifth
lens group, f.sub.6 is a focal length of said sixth lens group, and
L is a distance from said mask to said substrate, the following
conditions are satisfied:
f.sub.1 /L<0.8
-0.033<f.sub.2 /L
0.01<f.sub.3 /L<1.0
f.sub.4 /L<-0.005
0.01<f.sub.5 /L<0.9
0.02<f.sub.6 /L<1.6.
49. An exposure apparatus according to claim 48, wherein a
magnification of said projection optical system is 1/5.
50. An exposure apparatus according to claim 48, wherein said first
lens group has at least two positive lenses, said third lens group
has at least three positive lenses, said fourth lens group has at
least three negative lenses, said fifth lens group has at least
five positive lenses and at least one negative lens, and said sixth
lens group has at least one positive lens.
51. An exposure apparatus according to claim 50, wherein when I is
an axial distance from said first object to a first-object-side
focal point of said entire projection optical system and L is the
distance from said first object to said second object, the
following condition is satisfied:
52. An exposure apparatus according to claim 51, wherein said fifth
lens group has a negative meniscus lens, and a positive lens
disposed as adjacent to a concave surface of said negative meniscus
lens and having a convex surface opposed to the concave surface of
said negative meniscus lens, and
wherein when r.sub.5n is a radius of curvature of the concave
surface of said negative meniscus lens in said fifth lens group and
r.sub.5P is a radius of curvature of the convex surface, opposed to
the concave surface of the negative meniscus lens, of the positive
lens disposed as adjacent to the concave surface of said negative
meniscus lens in said fifth lens group, the following condition is
satisfied:
53. An exposure apparatus according to claim 52, wherein said
negative meniscus lens and said positive lens adjacent to the
concave surface of said negative meniscus lens are disposed between
at least one positive lens in said fifth lens group and at least
one positive lens in said fifth lens group.
54. An exposure apparatus according to claim 51, wherein said fifth
lens group comprises a negative lens placed as closest to the
second object and having a concave surface opposed to the second
object.
55. An exposure apparatus according to claim 54, wherein when
r.sub.6F is a radius of curvature of a lens surface closest to the
first object in said sixth lens group and d.sub.6 is an axial
distance from the lens surface closest to the first object in said
sixth lens group to the second object, the following condition is
satisfied:
56. An exposure apparatus according to claim 51, wherein when
f.sub.22 is a focal length of the second lens with the negative
refracting power in said second lens group and f.sub.23 is a focal
length of the third lens with the negative refracting power in said
second lens group, the following condition is satisfied:
57. An exposure apparatus according to claim 51, wherein when
f.sub.21 is a focal length of the first lens with the positive
refracting power in the intermediate lens group in said second lens
group and L is the distance from said first object to said second
object, the following condition is satisfied:
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure apparatus having a
projection optical system for projecting a pattern of a first
object onto a photosensitive substrate etc. as a second object, and
more particularly to a projection optical system suitably
applicable to projection exposure of a pattern for semiconductor or
liquid crystal formed on a reticle (mask) as the first object onto
the substrate (semiconductor wafer, plate, etc.) as the second
object.
2. Related Background Art
As the patterns of integrated circuits become finer and finer, the
resolving power required for the exposure apparatus used in
printing of wafer also becomes higher and higher. In addition to
the improvement in resolving power, the projection optical systems
of the exposure apparatus are required to decrease image stress. In
order to get ready for the finer tendency of transfer patterns,
light sources for exposure have recently been changing from those
emitting the light of exposure wavelength of the g-line (436 nm) to
those emitting the light of exposure wavelength of the i-line (365
nm) that are mainly used at present. Further, a trend is to use
light sources emitting shorter wavelengths, for example the excimer
laser (KrF:248 nm, ArF:193 nm).
Here, the image stress includes those due to bowing etc. of the
printed wafer on the image side of projection optical system and
those due to bowing etc. of the reticle with circuit pattern etc.
written therein, on the object side of projection optical system,
as well as distortion caused by the projection optical system.
With a recent further progress of fineness tendency of transfer
patterns, demands to decrease the image stress are also becoming
harder.
Then, in order to decrease effects of the wafer bowing on the image
stress, the conventional technology has employed the so-called
image-side telecentric optical system that located the exit pupil
position at a farther point on the image side of projection optical
system.
On the other hand, the image stress due to the bowing of reticle
can also be reduced by employing a so-called object-side
telecentric optical system that locates the entrance pupil position
of projection optical system at a farther point from the object
plane, and there are suggestions to locate the entrance pupil
position of projection optical system at a relatively far position
from the object plane as described. Examples of those suggestions
are described for example in Japanese Laid-open Patent Applications
No. 63-118115 and No. 5-173065 and U.S. Pat. No. 5,260,832.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a high-performance
projection optical system which can achieve the bitelecentricity in
a compact design as securing a wide exposure area and a large
numerical aperture and which can be well corrected for aberrations,
particularly which can be very well corrected for distortion. The
projection optical system can be applied to an exposure
apparatus.
To achieve the above object, an exposure apparatus according to the
present invention comprises at least a wafer stage allowing a
photosensitive substrate to be held on a main surface thereof, an
illumination optical system for emitting exposure light of a
predetermined wavelength and transferring a predetermined pattern
of a mask (reticle) onto the substrate, a projection optical system
provided between a first surface on which the mask as a first
object is disposed and a second surface on which a surface of the
substrate as a second object is corresponded, for projecting an
image of the pattern of the mask onto the substrate. The
illumination optical system includes an alignment optical system
for adjusting a relative positions between the mask and the wafer,
and the mask is disposed on a reticle stage which is movable in
parallel with respect to the main surface of the wafer stage. The
projection optical system has a space permitting an aperture stop
to be set therein. The photosensitive substrate comprises a wafer
such as a silicon wafer or a glass plate, etc., and a
photosensitive material such as a photoresist or the like coating a
surface of the wafer. In particular, as shown in FIG. 1, the
projection optical system includes a first lens group (G.sub.1)
with a positive refracting power, a second lens group (G.sub.2)
with a negative refracting power, a third lens group (G.sub.3) with
a positive refracting power, a fourth lens group (G.sub.4) with a
negative refracting power, a fifth lens group (G.sub.5) with a
positive refracting power, and a sixth lens group (G.sub.6) with a
positive refracting power in order from the side of the first
object (for example, a mask).
The second lens group (G.sub.2) comprises a front lens (L.sub.2F)
with a negative refracting power disposed as closest to the first
object and shaded with a concave surface to the second object, a
rear lens (L.sub.2R) of a negative meniscus shape disposed as
closest to the substrate and shaped with a concave surface to the
mask, and an intermediate lens group (G.sub.2M) disposed between
the front lens (L.sub.2F) and the rear lens (L.sub.2R). In
particular, the intermediate lens group (G.sub.2M) has a first lens
(L.sub.M1) with a positive refracting power, a second lens
(L.sub.M2) with a negative refracting power, and a third lens
(L.sub.M3) with a negative refracting power in order from the side
of the first object.
Further, the projection optical system according to the present
invention is arranged to satisfy the following conditions (1) to
(6) when f.sub.1 is a focal length of the first lens group
(G.sub.1), f.sub.2 is a focal length of the second lens group
(G.sub.2), f.sub.3 is a focal length of the third lens group
(G.sub.3), f.sub.4 is a focal length of the fourth lens group
(G.sub.4), f.sub.5 is a focal length of the fifth lens group
(G.sub.5), f.sub.6 is a focal length of the sixth lens group
(G.sub.6), and L is a distance from the first object to the second
object:
(1) f.sub.1 /L<0.8
(2) -0.033<f.sub.2 /L
(3) 0.01<f.sub.3 /L<1.0
(4) f.sub.4 /L<-0.005
(5) 0.01<f.sub.5 /L<0.9
(6) 0.02<f.sub.6 /L<1.6.
The projection optical system is so arranged as to have at least
the first lens group (G.sub.1) with positive refracting power, the
second lens group (G.sub.2) with negative refracting power, the
third lens group (G.sub.3) with positive refracting power, the
fourth lens group (G.sub.4) with negative refracting power, the
fifth lens group (G.sub.5) with positive refracting power, and the
sixth lens group (G.sub.6) with positive refracting power in the
named order from the first object side.
First, the first lens group (G.sub.1) with positive refracting
power contributes mainly to a correction of distortion while
maintaining telecentricity, and specifically, the first lens group
(G.sub.1) is arranged to generate a positive distortion to correct
in a good balance negative distortions caused by the plurality of
lens groups located on the second object side after the first lens
group (G.sub.1). The second lens group (G.sub.2) with negative
refracting power and the fourth lens group (G.sub.4) with negative
refracting power contribute mainly to a correction of Petzval sum
to make the image plane flat. The two lens groups of the second
lens group (G.sub.2) with negative refracting power and the third
lens group (G.sub.3) with positive refracting power form an inverse
telescopic system to contribute to guarantee of back focus (a
distance from an optical surface such as a lens surface closest to
the second object in the projection optical system to the second
object) in the projection optical system. The fifth lens group
(G.sub.5) with positive refracting power and the sixth lens group
(G.sub.6) similarly with positive refracting power contribute
mainly to suppressing generation of distortion and suppressing
generation particularly of spherical aberration as much as possible
in order to fully support high NA structure on the second object
side.
Based on the above arrangement, the front lens (L.sub.2F) with the
negative refracting power disposed as closest to the first object
in the second lens group (G.sub.2) and shaped with the concave
surface to the second object contributes to correction for
curvature of field and coma, and the rear lens (L.sub.2R) of the
negative meniscus shape disposed as closest to the second object in
the second lens group (G.sub.2) and shaped with the concave surface
to the first object contributes mainly to correction for coma. The
rear lens (L.sub.2R) also contributes to correction for curvature
of field. Further, in the intermediate lens group (G.sub.2M)
disposed between the front lens (L.sub.2F) and the rear lens
(L.sub.2R), the first lens (L.sub.M1) with the positive refracting
power contributes to correction for negative distortion generated
by the second lens (L.sub.M2) and third lens (L.sub.M3) of the
negative refracting powers greatly contributing to correction for
curvature of field.
Condition (1) defines an optimum ratio between the focal length
f.sub.1 of the first lens group (G.sub.1) with the positive
refracting power and the distance (object-to-image distance) L from
the first object (reticle etc.) to the second object (wafer etc.).
This condition (1) is mainly for well-balanced correction for
distortion.
Above the upper limit of condition (1), large negative distortion
will appear. In order to achieve a compact design as securing a
reduction magnification and a wide exposure area and to achieve
good correction for distortion, the upper limit of condition (1) is
preferably set to 0.14, as f.sub.1 /L<0.14. In order to suppress
appearance of spherical aberration of pupil, the lower limit of
condition (1) is preferably set to 0.02, as 0.02<f.sub.1 /L.
Condition (2) defines an optimum ratio between the focal length
f.sub.2 of the second lens group (G.sub.2) with the negative
refracting power and the distance (object-to-image distance) L from
the first object (reticle etc.) to the second object (wafer etc.).
This condition (2) is a condition for achieving a compact design as
securing a wide exposure region and achieving good correction for
Petzval sum.
Here, below the lower limit of condition (2), it becomes difficult
to achieve the compact design as securing the wide exposure region
and positive Petzval sum will appear, thus not preferred. In order
to achieve further compact design or superior correction for
Petzval sum, the lower limit of condition (2) is preferably set to
-0.032, as -0.032<f.sub.2 /L. In order to suppress appearance of
negative distortion, the upper limit of condition (2) is preferably
set to -0.005, as f.sub.2 /L<-0.005.
Condition (3) defines an optimum ratio between the focal length
f.sub.3 of the third lens group (G.sub.3) with the positive
refracting power and the distance (object-to-image distance) L from
the first object (reticle etc.) to the second object (wafer etc.).
Here, below the lower limit of condition (3), the refractive power
of the second lens group (G.sub.2) or the fourth lens group
(G.sub.4) becomes too strong, resulting in giving rise to negative
distortion and coma in the second lens group (G.sub.2) or giving
rise to coma in the fourth lens group (G.sub.4). On the other hand,
above the upper limit of condition (3), the refractive power of the
second lens group (G.sub.2) or the fourth lens group (G.sub.4)
becomes too weak, failing to well correct Petzval sum.
Condition (4) defines an optimum ratio between the focal length
f.sub.4 of the fourth lens group (G.sub.4) with the negative
refracting power and the distance (object-to-image distance) L from
the first object (reticle etc.) to the second object (wafer
etc.).
Here, above the upper limit of condition (4), coma will appear,
thus not preferred. Further, in order to suppress appearance of
coma, the upper limit of condition (4) is preferably set to -0.047,
as f.sub.4 /L<-0.047.
In order to well correct spherical aberration, the lower limit of
condition (4) is preferably set to -0.098, as -0.098<f.sub.4
/L.
Condition (5) defines an optimum ratio between the focal length
f.sub.5 of the fifth lens group (G.sub.5) with the positive
refracting power and the distance (object-to-image distance) L from
the first object (reticle etc.) to the second object (wafer etc.).
This condition (5) is for achieving well-balanced correction for
spherical aberration, distortion, and Petzval sum as maintaining a
large numerical aperture. Below the lower limit of this condition
(5), the refracting power of the fifth lens group (G.sub.5) becomes
too strong, resulting in giving rise to great negative spherical
aberration in addition to negative distortion in the fifth lens
group (G.sub.5). Above the upper limit of this condition (5), the
refracting power of the fifth lens group (G.sub.5) becomes too
weak, which inevitably weakens the refracting power of the fourth
lens group (G.sub.4) with the negative refracting power. As a
consequence, Petzval sum will not be well corrected.
Condition (6) defines an optimum ratio between the focal length
f.sub.6 of the sixth lens group (G.sub.6) with the positive
refracting power and the distance (object-to-image distance) L from
the first object (reticle etc.) to the second object (wafer etc.).
This condition (6) is for suppressing appearance of higher-order
spherical aberration and negative distortion as maintaining a large
numerical aperture. Below the lower limit of this condition (6),
the sixth lens group (G.sub.6) itself gives rise to great negative
distortion; above the upper limit of this condition (6),
higher-order spherical aberration will appear.
On the basis of the above composition it is preferred that when I
is an axial distance from the first object to a first-object-side
focal point F of the entire projection optical system and L is the
distance from the first object to the second object, the following
condition be satisfied:
The condition (7) defines an optimum ratio between the axial
distance I from the first object to the first-object-side focal
point F of the entire projection optical system and the distance
(object-image distance) L from the first object (reticle etc.) to
the second object (wafer etc.). Here, the first-object-side focal
point F of the entire projection optical system means an
intersecting point of outgoing light from the projection optical
system with the optical axis after collimated light beams are let
to enter the projection optical system on the second object side in
the paraxial region with respect to the optical axis of the
projection optical system and when the light beams in the paraxial
region are outgoing from the projection optical system.
Below the lower limit of this condition (7) the first-object-side
telecentricity of the projection optical system will become
considerably destroyed, so that changes of magnification and
distortion due to an axial deviation of the first object will
become large. As a result, it becomes difficult to faithfully
project an image of the first object at a desired magnification
onto the second object. In order to fully suppress the changes of
magnification and distortion due to the axial deviation of the
first object, the lower limit of the above condition (7) is
preferably set to 1.7, i.e., 1.7<I/L. Further, in order to
correct a spherical aberration and a distortion of the pupil both
in a good balance while maintaining the compact design of the
projection optical system, the upper limit of the above condition
(7) is preferably set to 6.8, i.e., I/L<6.8.
It is also preferred that the fourth lens group (G.sub.4) have a
front lens group disposed as closest to the first object and a rear
lens group disposed as closest to the second object, that an
intermediate lens group having a first negative lens (L.sub.43) and
a second negative lens (L.sub.44) in order from the side of the
first object be disposed between the front lens group in the fourth
lens group (G.sub.4) and the rear lens group in the fourth lens
group (G.sub.4), that the front lens group have two negative
meniscus lenses (L.sub.41, L.sub.42) each shaped with a concave
surface to the second object, that the rear lens group has a
negative lens (L.sub.46) with a concave surface to the first
object, and that when f.sub.4A is a focal length of the first
negative lens (L.sub.43) in the fourth lens group (G.sub.4) and
f.sub.4B is a focal length of the second negative lens (L.sub.44)
in the fourth lens group (G.sub.4), the following condition be
satisfied:
Below the lower limit of condition (8), the refractive power of the
first negative lens (L.sub.43) becomes strong relative to the
refractive power of the second negative lens (L.sub.44), so that
the first negative lens (L.sub.43) will give rise to higher-order
spherical aberration and higher-order coma. In order to suppress
appearance of the higher-order spherical aberration and
higher-order coma, the lower limit of the above condition (8) is
preferably set to 0.1, as 0.1<f.sub.4A /f.sub.4B. On the other
hand, above the upper limit of condition (8), the refracting power
of the second negative lens (L.sub.44) becomes strong relative to
the refracting power of the first negative lens (L.sub.43), so that
the second negative lens (L.sub.44) will give rise to higher-order
spherical aberration and higher-order coma. In order to further
suppress appearance of higher-order spherical aberration and
higher-order coma, the upper limit of the above condition (8) is
preferably set to 10, as f.sub.4A /f.sub.4B <10.
It is also preferred that when r.sub.2Ff is a radius of curvature
of a first-object-side surface of the front lens (L.sub.2 F) and
r.sub.2Fr is a radius of curvature of a second-object-side surface
of the front lens (L.sub.2F), the front lens (L.sub.2F) in the
second lens group (G.sub.2) satisfy the following condition:
Below the lower limit of this condition (9), sufficient correction
for spherical aberration of pupil becomes impossible, thus not
preferred. On the other hand, above the upper limit of this
condition (9), coma will appear, thus not preferred.
It is also preferred that the fourth lens group (G.sub.4) have a
front lens group having a negative lens (L.sub.41) disposed as
closest to the first object and shaped with a concave surface to
the second object, and a rear lens group having a negative lens
(L.sub.46) disposed as closest to the second object and shaped with
a concave surface to the first object, that an intermediate lens
group having at least a negative lens (L.sub.44) and a positive
lens (L.sub.45) with a convex surface adjacent to a concave surface
of the negative lens (L.sub.44) be disposed between the front lens
group in the fourth lens group (G.sub.4) and the rear lens group in
the fourth lens group (G.sub.4), and that when r.sub.4N is a radius
of curvature of the concave surface of the negative lens (L.sub.44)
in the intermediate lens group and r.sub.4P is a radius of
curvature of the convex surface of the positive lens (L.sub.45) in
the intermediate lens group, the following condition be
satisfied:
provided that when L is the distance from the first object to the
second object, the concave surface of the negative lens (L.sub.44)
in the intermediate lens group or the convex surface of the
positive lens (L.sub.45) in the intermediate lens group satisfies
at least one of the following conditions:
Conditions (10) to (12) define an optimum configuration of a gas
lens formed by the concave surface of the negative lens (L.sub.44)
in the intermediate lens group and the convex surface of the
positive lens (L.sub.45) in the intermediate lens group. When
condition (11) or (12) is satisfied, this gas lens can correct
higher-order spherical aberration. For further correction of
higher-order spherical aberration, the upper limits of condition
(11) and condition (12) are preferably set to 0.8, as
.vertline.r.sub.4N /L.vertline.<0.8 and .vertline.r.sub.4P
/L.vertline.<0.8. Here, above the upper limit or below the lower
limit of condition (10), coma will appear, thus not preferred. If
neither condition (11) nor condition (12) is satisfied, correction
for higher-order spherical aberration is impossible even if
condition (10) is satisfied, thus not preferred.
It is also preferred that when f.sub.22 is a focal length of the
second lens (L.sub.M2) with the negative refracting power in the
second lens group (G.sub.2) and f.sub.23 is a focal length of the
third lens (L.sub.M3) with the negative refracting power in the
second lens group (G.sub.2), the following condition be
satisfied:
Below the lower limit of the condition (13) the refracting power of
the second negative lens (L.sub.M2) becomes strong relative to the
refracting power of the third negative lens (L.sub.M3), so that the
second negative lens (L.sub.M2) generates a large coma and a large
negative distortion. In order to correct the negative distortion in
a better balance, the lower limit of the above condition (13) is
preferably set to 0.7, i.e., 0.7<f.sub.22 /f.sub.23. Above the
upper limit of this condition (13) the refracting power of the
third negative lens (L.sub.M3) becomes strong relative to the
refracting power of the second negative lens (L.sub.M2), so that
the third negative lens generates a large coma and a large negative
distortion. In order to correct the negative distortion in a better
balance while well correcting the coma, the upper limit of the
above condition (13) is preferably set to 1.5, i.e., f.sub.24
/f.sub.23 <1.5.
It is also preferred that the fifth lens group (G.sub.5) have a
negative meniscus lens (for example, L.sub.54), and a positive lens
(for example, L.sub.53) disposed as adjacent to a concave surface
of the negative meniscus lens and having a convex surface opposed
to the concave surface of the negative meniscus lens and that when
r.sub.5n is a radius of curvature of the concave surface of the
negative meniscus lens in the fifth lens group (G.sub.5) and
r.sub.5P is a radius of curvature of the convex surface, opposed to
the concave surface of the negative meniscus lens, of the positive
lens disposed as adjacent to the concave surface of the negative
meniscus lens in the fifth lens group (G.sub.5), the following
condition be satisfied:
In this case, it is preferred that the negative meniscus lens (for
example, L.sub.54) and the positive lens (L.sub.53) adjacent to the
concave surface of the negative meniscus lens be disposed between
at least one positive lens (for example, L.sub.52) in the fifth
lens group G.sub.5 and at least one positive lens (for example,
L.sub.55) in the fifth lens group (G.sub.5).
In this case, in order to suppress the negative distortion without
generating the higher-order spherical aberrations in the lens
(L.sub.61) located closest to the first object in the sixth lens
group (G.sub.6), it is desirable that the lens surface closest to
the first object have a shape with a convex surface to the first
object and that the following condition be satisfied when a radius
of curvature on the second object side, of the negative lens
(L.sub.58) placed as closest to the second object in the fifth lens
group (G.sub.5) is r.sub.5R and a radius of curvature on the first
object side, of the lens (L.sub.61) placed as closest to the first
object in the sixth lens group (G.sub.6) is r.sub.6F.
This condition (15) defines an optimum shape of a gas lens formed
between the fifth lens group (G.sub.5) and the sixth lens group
(G.sub.6). Below the lower limit of this condition (15) a curvature
of the second-object-side concave surface of the negative lens
(L.sub.58) located closest to the second object in the fifth lens
group (G.sub.5) becomes too strong, thereby generating higher-order
comas. Above the upper limit of this condition (15) refracting
power of the gas lens itself formed between the fifth lens group
(G.sub.5) and the sixth lens group (G.sub.6) becomes weak, so that
a quantity of the positive distortion generated by this gas lens
becomes small, which makes it difficult to well correct a negative
distortion generated by the positive lens in the fifth lens group
(G.sub.5). In order to fully suppress the generation of
higher-order comas, the lower limit of the above condition (15) is
preferably set to -0.30, i.e., -0.30<(r.sub.5R
-r.sub.6F)/(r.sub.5R +r.sub.6F).
Also, it is further preferable that the following condition be
satisfied when a lens group separation between the fifth lens group
(G.sub.5) and the sixth lens group (G.sub.6) is d.sub.56 and the
distance from the first object to the second object is L.
Above the upper limit of this condition (16), the lens group
separation between the fifth lens group (G.sub.5) and the sixth
lens group (G.sub.6) becomes too large, so that a quantity of the
positive distortion generated becomes small. As a result, it
becomes difficult to correct the negative distortion generated by
the positive lens in the fifth lens group (G.sub.5) in a good
balance.
Also, it is more preferable that the following condition be
satisfied when a radius of curvature of the lens surface closest to
the first object in the sixth lens group (G.sub.6) is r.sub.6F and
an axial distance from the lens surface closest to the first object
in the sixth lens group (G.sub.6) to the second object is
d.sub.6.
Below the lower limit of this condition (17), the positive
refracting power of the lens surface closest to the first object in
the sixth lens group (G.sub.6) becomes too strong, so that a large
negative distortion and a large coma are generated. Above the upper
limit of this condition (17), the positive refracting power of the
lens surface closest to the first object in the sixth lens group
(G.sub.6) becomes too weak, thus generating a large coma. In order
to further suppress the generation of coma, the lower limit of the
condition (17) is preferably set to 0.84, i.e., 0.84<d.sub.6
/r.sub.6 F.
Also, it is to be more desired that said fifth lens group (G.sub.5)
have a negative lens (L.sub.58) placed as closest to the second
object and having a concave surface opposed to the second object
and that the following condition be satisfied when a radius of
curvature on the first object side in the negative lens (L.sub.58)
closest to the second object in said fifth lens group (G.sub.5) is
r.sub.5F and a radius of curvature on the second object side in the
negative lens (L.sub.58) closest to the second object in said fifth
lens group (G.sub.5) is r.sub.5R :
Below the lower limit of this condition (18), it becomes difficult
to correct both the Petzval sum and the coma; above the upper limit
of this condition (18), large higher-order comas appear, which is
not preferable. In order to further prevent the generation of
higher-order comas, the upper limit of the condition (18) is
preferably set to 0.93, i.e., (r.sub.5F -r.sub.5R)/(r.sub.5F
+r.sub.5R)<0.93.
It is more desired that when f.sub.21 is a focal length of the
first lens (L.sub.M1) with the positive refracting power in the
intermediate lens group (G.sub.2M) in the second lens group
(G.sub.2) and L is the distance from the first object to the second
object, the following condition be satisfied:
Below the lower limit of condition (19), positive distortion will
appear; above the upper limit of condition (19), negative
distortion will appear, either of which is thus not preferred.
Further, in order to further correct the negative distortion, the
second-object-side lens surface of the first lens (L.sub.M1) is
preferably formed in a lens configuration shaped with a convex
surface facing the second object.
It is also preferred that when f.sub.2F is a focal length of the
front lens (L.sub.2F) with the negative refracting power disposed
as closest to the first object in the second lens group (G.sub.2)
and shaped with the concave surface to the second object and
f.sub.2R is a focal length of the rear lens (L.sub.2R) with the
negative refracting power disposed as closest to the second object
in the second lens group (G.sub.2) and shaped with the concave
surface to the first object, the following condition be
satisfied:
Also, the front lens (L.sub.2F) and the rear lens (L.sub.2R) in the
second lens group (G.sub.2) preferably satisfy the following
condition when the focal length of the front lens (L.sub.2F) placed
as closest to the first object in the second lens group (G.sub.2)
and having the negative refracting power with a concave surface to
the second object is f.sub.2F and the focal length of the rear lens
(L.sub.2R) placed as closest to the second object in the second
lens group (G.sub.2) and having the negative refracting power with
a concave surface to the second object is f.sub.2R.
The condition (20) defines an optimum ratio between the focal
length f.sub.2R of the rear lens (L.sub.2R) in the second lens
group (G.sub.2) and the focal length f.sub.2F of the front lens
(L.sub.2F) in the second lens group (G.sub.2). Below the lower
limit and above the upper limit of this condition (20), a balance
is destroyed for refracting power of the first lens group (G.sub.1)
or the third lens group (G.sub.3), which makes it difficult to
correct the distortion well or to correct the Petzval sum and the
astigmatism simultaneously well.
In order to further well correct Petzval sum, the intermediate lens
group (G.sub.2M) in the second lens group (G.sub.2) preferably has
a negative refracting power.
For the above lens groups to achieve satisfactory aberration
correction functions, specifically, they are desired to be
constructed in the following arrangements.
First, for the first lens group (G.sub.1) to have a function to
suppress appearance of higher-order distortion and appearance of
spherical aberration of pupil, the first lens group (G.sub.1)
preferably has at least two positive lenses; for the third lens
group (G.sub.3) to have a function to suppress degradation of
spherical aberration and Petzval sum, the third lens group
(G.sub.3) preferably has at least three positive lenses; further,
for the fourth lens group (G.sub.4) to have a function to suppress
appearance of coma as correcting Petzval sum, the fourth lens group
(G.sub.4) preferably has at least three negative lenses. For the
fifth lens group (G.sub.5) to have a function to suppress
appearance of negative distortion and spherical aberration, the
fifth lens group (G.sub.5) preferably has at least five positive
lenses; further, for the fifth lens group (G.sub.5) to have a
function to correct negative distortion and Petzval sum, the fifth
lens group (G.sub.5) preferably has at least one negative lens. For
the sixth lens group (G.sub.6) to effect focus on the second object
so as not to give rise to large spherical aberration, the sixth
lens group (G.sub.6) preferably has at least one positive lens.
For further compact design, the intermediate lens group in the
second lens group desirably comprises only two negative lenses.
For the sixth lens group (G.sub.6) to have a function to further
suppress appearance of negative distortion, the sixth lens group
(G.sub.6) is preferably arranged to comprise three or less lenses
including at least one lens surface satisfying the following
condition (21).
where
.PHI.: a refractive power of the lens surface; and
L: the distance (object-to-image distance) from the first object to
the second object.
The refractive power of lens surface, stated here, is given by the
following equation where r is a radius of curvature of the lens
surface, n.sub.1 a refractive index of a medium on the first object
side of the lens surface, and n.sub.2 a refractive index of a
medium on the second object side of the lens surface.
Here, if there are four or more lenses having the lens surface
satisfying this condition (21), the number of lens surfaces with
some curvature, located near the second object, becomes increased,
which generates the distortion, thus not preferable.
The present invention will become more fully understood from the
detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become
apparent from the detailed description given hereinafter. However,
it should be understood that the detailed description and specific
examples, while indicating preferred embodiments of the invention,
are given by way of illustration only, since various changes and
modifications within the spirit and scope of the invention will
become apparent to those skilled in the art form this detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a drawing to show parameters defined in embodiments of
the present invention.
FIG. 2 is a drawing to show schematic structure of an exposure
apparatus to which the projection optical system according to the
present invention is applied.
FIG. 3 is a lens arrangement drawing of the projection optical
system in the first embodiment according to the present
invention.
FIG. 4 is a lens arrangement drawing of the projection optical
system in the second embodiment according to the present
invention.
FIG. 5 is a lens arrangement drawing of the projection optical
system in the third embodiment according to the present
invention.
FIG. 6 is a lens arrangement drawing of the projection optical
system in the fourth embodiment according to the present
invention.
FIGS. 7-10 are aberration diagrams to show aberrations in the
projection optical system of the first embodiment.
FIGS. 11-14 are aberration diagrams to show aberrations in the
projection optical system of the second embodiment.
FIGS. 15-18 are aberration diagrams to show aberrations in the
projection optical system of the third embodiment.
FIGS. 19-22 are aberration diagrams to show aberrations in the
projection optical system of the fourth embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Various embodiments of the projection optical system according to
the present invention will be described with reference to the
drawings. In the examples, the present invention is applied to the
projection optical system in the projection exposure apparatus for
projecting an image of patterns of reticle onto a wafer coated with
a photoresist. FIG. 2 shows a basic structure of the exposure
apparatus according to the present invention. As shown in FIG. 2,
an exposure apparatus of the present invention comprises at least a
wafer stage 3 allowing a photosensitive substrate W to be held on a
main surface 3a thereof, an illumination optical system 1 for
emitting exposure light of a predetermined wavelength and
transferring a predetermined pattern of a mask (reticle R) onto the
substrate W, a light source 100 for supplying an exposure light to
the illumination optical system 1, a projection optical system 5
provided between a first surface P1 (object plane) on which the
mask R is disposed and a second surface P2 (image plane) to which a
surface of the substrate W is corresponded, for projecting an image
of the pattern of the mask R onto the substrate W. The illumination
optical system 1 includes an alignment optical system 110 for
adjusting a relative positions between the mask R and the wafer W,
and the mask R is disposed on a reticle stage 2 which is movable in
parallel with respect to the main surface of the wafer stage 3. A
reticle exchange system 200 conveys and changes a reticle (mask R)
to be set on the reticle stage 2. The reticle exchange system 200
includes a stage driver for moving the reticle stage 2 in parallel
with respect to the main surface 3a of the wafer stage 3. The
projection optical system 5 has a space permitting an aperture stop
6 to be set therein. The sensitive substrate W comprises a wafer 8
such as a silicon wafer or a glass plate, etc., and a
photosensitive material 7 such as a photoresist or the like coating
a surface of the wafer 8. The wafer stage 3 is moved in parallel
with respect to a object plane P1 by a stage control system 300.
Further, since a main control section 400 such as a computer system
controls the light source 100, the reticle exchange system 200, the
stage control system 300 or the like, the exposure apparatus can
perform a harmonious action as a whole.
The techniques relating to an exposure apparatus of the present
invention are described, for example, in U.S. patent applications
Ser. Nos. 255,927, 260,398, 299,305, U.S. Pat. Nos. 4,497,015,
4,666,273, 5,194,893, 5,253,110, 5,333,035, 5,365,051, 5,379,091,
or the like. The reference of U.S. patent application Ser. No.
255,927 teaches an illumination optical system (using a laser
source) applied to a scan type exposure apparatus. The reference of
U.S. patent application Ser. No. 260,398 teaches an illumination
optical system (using a lamp source) applied to a scan type
exposure apparatus. The reference of U.S. patent application Ser.
No. 299,305 teaches an alignment optical system applied to a scan
type exposure apparatus. The reference of U.S. Pat. No. 4,497,015
teaches an illumination optical system (using a lamp source)
applied to a scan type exposure apparatus. The reference of U.S.
Pat. No. 4,666,273 teaches a step-and repeat type exposure
apparatus capable of using the projection optical system of the
present invention. The reference of U.S. Pat. No. 5,194,893 teaches
an illumination optical system, an illumination region, mask-side
and reticle-side interferometers, a focusing optical system,
alignment optical system, or the like. The reference of U.S. Pat.
No. 5,253,110 teaches an illumination optical system (using a laser
source) applied to a step-and-repeat type exposure apparatus. The
'110 reference can be applied to a scan type exposure apparatus.
The reference of U.S. Pat. No. 5,333,035 teaches an application of
an illumination optical system applied to an exposure apparatus.
The reference of U.S. Pat. No. 5,365,051 teaches a auto-focusing
system applied to an exposure apparatus. The reference of U.S. Pat.
No. 5,379,091 teaches an illumination optical system (using a laser
source) applied to a scan type exposure apparatus.
As described above, a reticle R (first object) as a projection mask
with specific circuit patterns formed therein is disposed on the
object plane (P1) of the projection optical system 1 and a wafer W
(second object) as a substrate on the image plane (P2) of the
projection optical system 1. Here, the reticle R is held on a
reticle stage 2 and the wafer W on a wafer stage 3 arranged as
movable on a two-dimensional basis. Disposed above the reticle R is
an illumination optical system 1 for uniformly illuminating the
reticle R.
In the above arrangement, light supplied from the light source 100
through the illumination optical system 1 illuminates the reticle R
to form an image at the pupil position of the projection optical
system 1 (the position of aperture stop 6). Namely, the
illumination optical system 1 uniformly illuminates the reticle R
under Kohler illumination. Then the pattern image of reticle R
illuminated under Kohler illumination is projected (or transferred)
onto the wafer W.
The present embodiment shows an example of which the light source
100 is a mercury lamp for supplying the i-line (365 nm). The
structure of the projection optical system in each embodiment will
be described by reference to FIG. 3 to FIG. 6. FIG. 3 to FIG. 6 are
lens structural drawings of the projection optical systems 1 in the
first to fourth embodiments, respectively, according to the present
invention.
As shown in FIG. 3 to FIG. 6, the projection optical system 1 in
each embodiment has a first lens group G.sub.1 with a positive
refractive power, a second lens group G.sub.2 with a negative
refractive power, a third lens group G.sub.3 with a positive
refractive power, a fourth lens group G.sub.4 with a negative
refractive power, a fifth lens group G.sub.5 with a positive
refractive power, and a sixth lens unit G.sub.6 with a positive
refractive power in order from the side of reticle R as a first
object, is arranged as substantially telecentric on the object side
(reticle R side) and on the image side (wafer W side), and has a
reduction magnification.
In the projection optical system 1 in each of the embodiments shown
in FIG. 3 to FIG. 6, an object-to-image distance (a distance along
the optical axis from the object plane to the image plane, or a
distance along the optical axis from the reticle R to wafer W) L is
1100, an image-side numerical aperture NA is 0.57, a projection
magnification .beta. is 1/5, and a diameter of an exposure area on
the wafer W is 31.2. The object-to-image distance L and the
diameter of the exposure area are expressed in a same unit, and the
unit corresponds to a unit of r and d shown in the following tables
1, 3, 5 and 7.
First described is a specific lens arrangement of the first
embodiment shown in FIG. 3. The first lens group G.sub.1 has a
negative meniscus lens L.sub.11 shaped with a concave surface to
the image, a positive lens (positive lens of a biconvex shape)
L.sub.12 shaped with a convex surface to the object, and two
positive lenses (positive lenses of biconvex shapes) L.sub.13,
L.sub.14 each shaped with a strong-curvature surface to the object
in order from the object side.
Further, the second lens group G.sub.2 has a negative lens
(negative lens of a biconcave shape: front lens) L.sub.2F disposed
as closest to the object and shaped with a concave surface to the
image, a negative meniscus lens (rear lens) L.sub.2R disposed as
closest to the image and shaped with a concave surface to the
object, and an intermediate lens group G.sub.2M with a negative
refractive power disposed between these negative lens L.sub.2F and
negative lens L.sub.2R. This intermediate lens group G.sub.2M has a
positive lens (positive lens of a biconvex shape: first lens)
L.sub.M1 shaped with a strong-curvature surface to the image, a
negative lens (negative lens of a biconcave shape: second lens)
L.sub.M2 shaped with a strong-curvature surface to the image, and a
negative lens (negative lens of a biconcave shape: third lens)
L.sub.M3 shaped with a strong-curvature surface to the object in
order from the object side.
The third lens group G.sub.3 has two positive lenses (positive
meniscus lenses) L.sub.31, L.sub.32 each shaped with a
strong-curvature surface to the image, a positive lens L.sub.33 of
a biconvex shape, a positive lens (positive lens of a biconvex
shape) L.sub.34 shaped with a strong-curvature surface to the
object, and a positive lens (positive meniscus lens) L.sub.35
shaped with a strong-curvature surface to the object in order from
the object side.
The fourth lens group G.sub.4 has two negative meniscus lenses
(front lens group) L.sub.41, L.sub.42 each shaped with a concave
surface to the image, a negative lens (negative meniscus lens:
first negative lens) L.sub.43 shaped with a concave surface to the
object, a negative lens (second negative lens: negative lens with a
concave surface to the image) L.sub.44 of a biconcave shape, a
positive lens (positive meniscus lens: positive lens having a
convex surface adjacent to the concave surface of the negative lens
L.sub.44) L.sub.45 shaped with a convex surface to the object, and
a negative lens (negative lens of a biconcave shape: rear lens
group) L.sub.46 shaped with a concave surface to the object in
order from the object side.
The fifth lens group G.sub.5 has two positive lenses (positive
lenses of biconvex shapes) L.sub.51, L.sub.52 each shaped with a
convex surface to the image, a positive lens L.sub.53 of a biconvex
shape, a negative meniscus lens L.sub.54 shaped with a concave
surface to the object, a positive lens L.sub.55 shaped with a
stronger-curvature surface to the object, two positive lenses
(positive meniscus lenses) L.sub.56, L.sub.57 each shaped with a
stronger-curvature surface to the object, and a negative meniscus
lens L.sub.58 shaped with a concave surface to the image in order
from the object side.
Further, the sixth lens group G.sub.6 is composed of a positive
lens (positive lens of a biconvex shape) L.sub.61 shaped with a
stronger-curvature surface to the object, and a negative lens
(negative lens of a biconcave shape) L.sub.62 shaped with a concave
surface to the object in order from the object side.
In the present embodiment, an aperture stop 6 is disposed between
the positive meniscus lens L.sub.45 with the convex surface to the
object and the negative lens L.sub.46 of the biconcave shape, that
is, between the intermediate lens group in the fourth lens group
G.sub.4 and the rear lens group in the fourth lens group
G.sub.4.
In the first lens group G.sub.1 in the present embodiment, the
concave surface of the negative meniscus lens L.sub.11 with the
concave surface to the image and the object-side lens surface of
the positive biconvex lens L.sub.12 have nearly equal curvatures
and are arranged as relatively close to each other, and these two
lens surfaces correct higher-order distortion.
Since the first lens L.sub.M1 with the positive refractive power in
the second lens group G.sub.2M is constructed in the biconvex shape
with the convex surface to the image and also with the other convex
surface to the object, it can suppress appearance of spherical
aberration of pupil.
Since the fourth lens group G.sub.4 is so arranged that the
negative meniscus lens L.sub.41 with the concave surface to the
image is disposed on the object side of the negative lens (negative
biconcave lens) L.sub.44 and that the negative lens L.sub.46 with
the concave surface to the object is disposed on the image side of
the negative lens (negative biconcave lens) L.sub.44, it can
correct Petzval sum as suppressing appearance of coma.
Since in the first embodiment the aperture stop 6 is placed between
the image-side concave surface of the negative meniscus lens
L.sub.41 and the object-side concave surface of the negative lens
L.sub.46 in the fourth lens group G.sub.4, the lens groups of from
the third lend group G.sub.3 to the sixth lens group G.sub.6 can be
arranged around the aperture stop 6 with a more or less reduction
magnification and without destroying the symmetry too much, thus
enabling to suppress asymmetric aberration, particularly coma and
distortion. Since the positive lens L.sub.53 in the fifth lens
group G.sub.5 has a convex surface opposed to the negative meniscus
lens L.sub.54 and the other lens surface on the opposite side to
the negative meniscus lens L.sub.54 is also a convex surface,
higher-order spherical aberration can be prevented from appearing
with an increase of numerical aperture.
The specific lens arrangement of the second embodiment shown in
FIG. 4 is similar to that of the first embodiment as shown in FIG.
3 and described above. The third lens group G.sub.3 in the second
embodiment is different from that in the first embodiment in that
the third lens group G.sub.3 is composed of two positive lenses
(positive meniscus lenses) L.sub.31, L.sub.32 each shaped with a
strong-curvature surface to the image, a positive lens L.sub.33 of
a biconvex shape, a positive lens (positive lens of a biconvex
shape) L.sub.34 shaped with a strong-curvature surface to the
object, and a positive lens (positive lens of a biconvex shape)
L.sub.35 shaped with a strong-curvature surface to the object in
order from the object side.
In the second embodiment, the fourth lens group G.sub.4 is
different from that in the first embodiment in that the fourth lens
group G.sub.4 is composed of two negative meniscus lenses (front
lens group) L.sub.41, L.sub.42 each shaped with a concave surface
to the image, a negative lens (negative lens of a biconcave shape:
first negative lens) L.sub.43 shaped with a concave surface to the
object, a negative lens (second negative lens: negative lens with a
concave surface to the image) L.sub.44 of a biconcave shape, a
positive lens (positive meniscus lens: positive lens having a
convex surface adjacent to the concave surface of the negative lens
L.sub.44) L.sub.45 shaped with a convex surface to the object, and
a negative lens (negative lens of a biconcave shape: rear lens
group) L.sub.46 shaped with a stronger concave surface to the
object in order from the object side, but the function thereof is
the same as that in the first embodiment as described above.
Further, the first and second lens groups G.sub.1, G.sub.2 and the
fifth and sixth lens groups G.sub.5, G.sub.6 in the second
embodiment achieve the same functions as those in the first
embodiment as described above.
The specific lens arrangement of the third embodiment shown in FIG.
5 is similar to that of the first embodiment shown in FIG. 3 and
described previously. The first lens group G.sub.1 of the present
embodiment is different from that of the first embodiment in that
the first lens group G.sub.1 is composed of a negative meniscus
lens L.sub.11 shaped with a concave surface to the image, a
positive lens (positive lens of a biconvex shape) L.sub.12 shaped
with a convex surface to the object, a positive lens (positive lens
of a plano-convex shape) L.sub.13 shaped with a strong-curvature
surface to the object, and a positive lens (positive lens of a
biconvex shape) L.sub.14 shaped with a strong-curvature surface to
the object in order from the object side, but the function thereof
is the same as that in the first embodiment as described
previously.
The second to sixth lens groups G.sub.2 -G.sub.6 in the third
embodiment achieve the same functions as those in the first
embodiment as described previously.
The specific lens arrangement of the fourth embodiment of FIG. 6 is
similar to that of the first embodiment shown in FIG. 3 and
described previously. The fourth lens group G.sub.4 in the present
embodiment is different from that of the first embodiment in that
the fourth lens group G.sub.4 is composed of two negative meniscus
lenses (front lens group) L.sub.41, L.sub.42 each with a concave
surface to the image, a negative lens (negative lens of a biconcave
shape: first negative lens) L.sub.43 shaped with a concave surface
to the object, a negative lens (second negative lens: negative lens
with a concave surface to the image) L.sub.44 of a biconcave shape,
a positive lens (positive meniscus lens: a positive lens having a
convex surface adjacent to the concave surface of the negative lens
L.sub.44) L.sub.45 shaped with a convex surface to the object, and
a negative lens (negative lens of a biconcave shape: rear lens
group) L.sub.46 shaped with a concave surface to the object in
order from the object side, but the function thereof is the same as
that in the first embodiment as described previously.
Further, in the fourth embodiment, the sixth lens group G.sub.6 is
different from that of the first embodiment in that the sixth lens
group G.sub.6 is composed of a positive lens (positive lens of a
biconvex shape) L.sub.61 shaped with a stronger-curvature surface
to the object and a negative lens (negative meniscus lens) L.sub.62
shaped with a concave surface to the object in order from the
object side.
The first to third lens groups G.sub.1 to G.sub.3 and the fifth
lens group G.sub.5 in the present embodiment achieve the same
functions as those in the first embodiment described
previously.
Table 1 to Table 8 to follow list values of specifications and
correspondent values to the conditions for the respective
embodiments in the present invention.
In the tables, left-end numerals represent orders from the object
side (reticle R side), r radii of curvatures of lens surfaces, d
separations between lens surfaces, n refractive indices of glass
materials for exposure wavelength .lambda. of 365 nm, d.sub.0 the
distance along the optical axis from the first object (reticle R)
to the lens surface (first lens surface) closest to the object
(reticle R) in the first lens group G.sub.1, .beta. the projection
magnification of projection optical system, Bf the distance along
the optical axis from the lens surface closest to the image (wafer
W) in the sixth lens group G.sub.6 to the image plane P2 (wafer W
plane), NA the numerical aperture on the image side (wafer W side),
of projection optical system, and L is the object-to-image distance
from the object plane P1 (reticle R plane) to the image plane P2
(wafer W plane). Further, in the tables, f.sub.1 represents the
focal length of the first lens group G.sub.1, f.sub.2 the focal
length of the second lens group G.sub.2, f.sub.3 the focal length
of the third lens group G.sub.3, f.sub.4 the focal length of the
fourth lens group G.sub.4, f.sub.5 the focal length of the fifth
lens group G.sub.5, f.sub.6 the focal length of the sixth lens
group G.sub.6, L the distance (object-to-image distance) from the
object plane (reticle plane) to the image plane (wafer plane), I
the axial distance from the first object (reticle) to the
first-object-side focal point F of the entire projection optical
system (provided that the first-object-side focal point F of the
entire projection optical system means an intersecting point of
emergent light with the optical axis when parallel light in the
paraxial region with respect to the optical axis of the projection
optical system is made incident from the second object side of the
projection optical system and the light in the paraxial region is
emergent from the projection optical system), f.sub.4A the focal
length of the first negative lens (L.sub.43) in the intermediate
lens group in the fourth lens group G.sub.4, f.sub.4 the focal
length of the second negative lens (L.sub.44) in the intermediate
lens group in the fourth lens group G.sub.4, r.sub.2Ff the radius
of curvature of the first-object-side lens surface of the front
lens L.sub.2F in the second lens group G.sub.2, R.sub.2Fr the
radius of curvature of the second-object-side lens surface of the
front lens L.sub.2F in the second lens group G.sub.2, r.sub.4N the
radius of curvature of the second-object-side concave surface of
the negative lens (L.sub.44) in the intermediate lens group in the
fourth lens group G.sub.4, r.sub.4P the radius of curvature of the
first-object-side convex surface of the positive lens (L.sub.45) in
the intermediate lens group in the fourth lens group G.sub.4,
f.sub.22 the focal length of the second lens with the negative
refractive power in the second lens group, f.sub.23 the focal
length of the third lens with the negative refractive power in the
second lens group G.sub.2, r.sub.5n the radius of curvature of the
concave surface in the negative meniscus lens in the fifth lens
group G.sub.5, r.sub.5p the radius of curvature of the convex
surface opposed to the concave surface of the negative meniscus
lens in the positive lens disposed as adjacent to the concave
surface of the negative meniscus lens in the fifth lens group
G.sub.5, r.sub.5R the radius of curvature of the second-object-side
surface of the negative lens disposed as closest to the second
object in the fifth lens group G.sub.5, r.sub.6F the radius of
curvature of the first-object-side surface of the lens disposed as
closest to the first object in the sixth lens group G.sub.6,
d.sub.56 the lens group separation between the fifth lens group
G.sub.5 and the sixth lens group G.sub.6, d.sub.6 the axial
distance from the lens surface closest to the first object in the
sixth lens group G.sub.6 to the second object, r.sub.5F the radius
of curvature of the first-object-side surface in the negative lens
disposed as closest to the second object in the fifth lens group
G.sub.5, f.sub.21 the focal length of the first lens with the
positive refractive power in the intermediate lens group G.sub.2M
in the second lens group G.sub.2, f.sub.2F the focal length of the
front lens with the negative refractive power disposed as closest
to the first object in the second lens group G.sub.2 and shaped
with the concave surface to the second object, and f.sub.2R the
focal length of the rear lens of the negative meniscus shape
disposed as closest to the second object in the second lens group
G.sub.2 and shaped with the concave surface to the object.
TABLE 1 ______________________________________ First Embodiment dO
= 94.97557 .beta.= 1/5 NA = 0.57 Bf = 22.68864 L = 1100 r d n 1
758.59372 18.01962 1.66638 2 273.07409 8.00000 3 407.25600 34.43806
1.53627 4 -305.98082 0.50000 5 200.00000 36.31512 1.53627 6
-950.89920 0.50000 7 251.35670 36.00000 1.53627 8 -1111.20100
5.00000 9 -3000.00000 13.00000 1.66638 10 103.53326 19.34714 11
583.43731 21.86239 1.53627 12 -202.73262 3.71513 13 -389.07550
13.00000 1.53627 14 118.39346 25.82991 15 -119.29984 13.00000
1.53627 16 228.68065 35.35939 17 -118.78231 15.61439 1.53627 18
-2000.00000 15.00000 19 -534.21970 30.58806 1.53627 20 -172.96367
0.50000 21 -3045.95900 30.55054 1.53627 22 -252.31005 0.50000 23
787.95642 31.33960 1.53627 24 -470.11486 0.50000 25 429.05519
31.10739 1.53627 26 -1033.56100 0.50000 27 276.54228 29.82671
1.53627 28 3383.80700 0.50000 29 200.56082 25.00000 1.53627 30
149.82206 51.17799 31 191.38232 25.00000 1.53627 32 122.34204
25.15581 33 -276.65501 13.00000 1.66638 34 -597.90043 9.14516 35
-190.18194 13.00000 1.66638 36 360.79756 3.75310 37 434.45763
13.00000 1.53627 38 643.56408 31.17056 39 -951.39487 20.00000
1.66638 40 360.75541 3.46004 41 395.41239 33.29191 1.53627 42
-229.24043 0.50000 43 405.02177 21.76952 1.53627 44 -1456.27300
0.50000 45 334.62149 34.87065 1.53627 46 -316.02886 8.19653 47
-226.66975 20.00000 1.66638 48 -421.19119 0.50000 49 245.00959
27.62592 1.53627 50 -6478.64400 0.50000 51 118.64887 24.82664
1.53627 52 182.84804 0.50000 53 106.97354 29.80517 1.53627 54
305.86346 2.86446 55 330.12685 13.00000 1.66638 56 65.69252 7.67289
57 76.63392 29.80077 1.53627 58 -405.45793 2.41289 59 -314.04117
20.42250 1.53627 60 1180.34006 (Bf)
______________________________________
TABLE 2 ______________________________________ Correspondent Values
to the Conditions for First Embodiment (1) f1 /L = 0.129 (2) f2 /L
= -0.0299 (3) f3 /L = 0.106 (4) f4 /L = -0.0697 (5) f5 /L = 0.0804
(6) f6 /L = 0.143 (7) I/L = 2.02 (8) f4A/f4B = 4.24 (9) (r2Ff -
r2Fr) / (r2Ff + r2Fr) = 1.07 (10) (r4N - r4P) / (r4N + r4PY) =
-0.0926 (11) .vertline.r4N/L.vertline. = 0.328 (12)
.vertline.r4P/L.vertline. = 0.395 (13) f22/f23 = 1.16 (14) (r5p -
r5n) / (r5p + r5n) = 0.165 (15) (r5R - r6F) / (r5R + r6F) = -0.0769
(16) d56/L = 0.00698 (17) d6 / r6F = 0.983 (18) (r5F - r5R) / (r5F
+ r5R) = 0.668 (19) f21/L = 0.258 (20) f2F/f2R = 0.635
______________________________________
TABLE 3 ______________________________________ Second Embodiment dO
= 98.09086 .beta. = 1/5 NA = 0.57 Bf = 22.68864 L = 1100 r d n 1
715.79825 18.01962 1.66638 2 257.11993 8.00000 3 402.81202 34.43806
1.53627 4 -298.91362 0.50000 5 200.00000 36.31512 1.53627 6
-811.20841 0.50000 7 202.30081 36.00000 1.53627 8 -912.77876
-0.24598 9 -3000.00000 13.00000 1.66638 10 100.16757 19.34714 11
515.50992 21.86239 1.53627 12 -211.08983 3.71513 13 -334.85048
13.00000 1.53627 14 119.28367 24.34073 15 -124.53825 13.00000
1.53627 16 196.56654 35.64064 17 -122.83913 15.61439 1.53627 18
-2000.00000 15.00000 19 -319.01403 30.58806 l.53627 20 -192.95790
0.50000 21 -1320.53000 30.55054 1.53627 22 -229.09627 0.50000 23
1670.41600 31.33960 1.53627 24 -355.67749 0.50000 25 505.94351
31.10739 l.53627 26 -669.94239 0.50000 27 272.78755 29.82671
1.53627 28 -11188.96200 0.50000 29 205.32433 25.00000 1.53627 30
156.91075 68.35861 31 170.81860 25.00000 1.53627 32 119.41166
25.17539 33 -221.51521 13.00000 1.66638 34 3749.27900 7.91441 35
-299.53056 13.00000 1.66638 36 360.79756 3.75310 37 434.45763
13.00000 1.53627 38 643.56408 18.53967 39 -6417.33300 20.00000
1.66638 40 300.16308 3.46004 41 329.77719 33.29191 1.53627 42
-264.12523 0.50000 43 804.85248 21.76952 1.53627 44 -784.29788
0.50000 45 273.73159 34.87065 1.53627 46 -325.58814 8.19653 47
-214.52517 20.00000 1.66638 48 -405.91293 0.50000 49 396.09997
27.62592 1.53627 50 -579.80514 0.50000 51 115.71351 24.82664
1.53627 52 255.34580 0.50000 53 104.86226 29.80517 1.53627 54
211.50003 2.86446 55 312.25500 13.00000 1.66638 56 66.11566 7.67289
57 76.78058 29.80077 1.53627 58 -437.18968 2.41289 59 -324.32040
20.42250 1.53627 60 2434.44700 (Bf)
______________________________________
TABLE 4 ______________________________________ Correspondent Values
to the Conditions for Second Embodiment (1) f1 /L = 0.119 (2) f2 /L
= -0.0292 (3) f3 /L = 0.111 (4) f4 /L = -0.0715 (5) f5 /L = 0.0806
(6) f6 /L = 0.140 (7) I/L = 2.02 (8) f4A/f4B = 1.29 (9) (r2Ff -
r2Fr) / (r2Ff + r2Fr) = 1.07 (10) (r4N - r4P) / (r4N + r4P) =
-0.0926 (11) .vertline.r4N/L.vertline.= 0.328 (12)
.vertline.r4P/L.vertline.= 0.395 (13) f22/f23 = 1.16 (14) (r5p -
r5n) / (rsp + r5n) = 0.206 (15) (r5R - r6F) / (r5R + r6F) = -0.114
(16) d56/L = 0.00698 (17) d6 /r6F = 0.981 (18) (r5F - r5R) / (r5F +
r5R) = 0.673 (19) f21/L = 0.257 (20) f2F/f2R = 0.593
______________________________________
TABLE 5 ______________________________________ Third Embodiment dO
= 105.97406 .beta. = 1/5 NA = 0.57 Bf = 21.09296 L = 1100 r d n 1
835.93450 19.00074 1.61298 2 349.00002 6.60188 3 493.73823 30.01023
1.61536 4 -364.99999 1.12825 5 189.67357 32.71424 1.61536 6 .infin.
1.25667 7 219.68925 26.27974 1.61536 8 -2935.50000 2.86486 9
-1456.03000 15.60000 1.61298 10 98.87901 25.83515 11 572.77742
19.48735 1.48734 12 -245.99492 3.28431 13 -517.01308 16.35209
1.61536 14 118.78195 22.95916 15 -151.83256 12.94478 1.61536 16
196.86505 33.74710 17 -129.25780 12.89677 1.61536 18 -491.95895
13.46314 19 -246.12435 22.58245 1.61536 20 -166.51997 0.39125 21
-1477.30500 28.55306 1.61536 22 -216.04701 0.72991 23 425.36937
33.51075 1.61536 24 -524.95999 0.96043 25 438.35798 25.74084
1.48734 26 -1678.66000 0.33363 27 292.51673 23.69782 1.48734 28
1518.72000 0.83738 29 218.42396 26.38775 1.48734 30 148.35403
33.09868 31 203.95726 27.76454 1.61536 32 133.43801 30.67100 33
-211.86216 13.01538 1.61298 34 -1024.57000 15.53690 35 -160.75584
13.15020 1.61298 36 270.91502 0.55149 37 250.92650 15.66663 1.48734
38 702.02996 23.07586 39 -827.25951 15.36200 1.61298 40 2298.00000
0.73901 41 2301.62000 27.62162 1.48734 42 -223.08205 0.51051 43
488.67440 34.23933 1.48734 44 -319.00802 0.49298 45 500.98379
34.15684 1.61536 46 -369.12909 9.55181 47 -242.59289 18.84686
1.61298 48 -613.52998 0.50392 49 347.10206 30.00332 1.61536 50
-1728.40000 0.49017 51 180.81644 30.27184 1.48734 52 728.32004
0.48766 53 119.02258 38.20547 1.48734 54 609.84003 3.61782 55
1650.31000 19.05217 1.61298 56 77.86795 17.17240 57 81.07073
30.61882 1.48734 58 -335.26499 2.16189 59 -316.96290 26.15191
1.61536 60 -848.55009 (Bf)
______________________________________
TABLE 6 ______________________________________ Correspondent Values
to the Conditions for Third Embodiment (1) f1 /L = 0.117 (2) f2 /L
= -0.0288 (3) f3 /L = 0.106 (4) f4 /L = -0.0762 (5) f5 /L = 0.0868
(6) f6 /L = 0.147 (7) I/L = 2.87 (8) f4A/f4B = 2.69 (9) (r2Ff -
r2Fr) / (r2Ff + r2Fr) = 1.15 (10) (r4N - r4P) / (r4N + r4P) =
0.0383 (11) .vertline.r4N/L.vertline. = 0.246 (12)
.vertline.r4P/L.vertline. = 0.228 (13) f22/f23 = 1.13 (14) (r5p -
r5n) / (r5p + r5n) = 0.207 (15) (r5R - r6F) / (r5R + r6F) = -0.0202
(16) d56/L = 0.0156 (17) d6 /r6F = 0.987 (18) (r5F - r5R) / (r5F +
r5R) = 0.910 (19) f21/L = 0.324 (20) f2F/f2R = 0.521
______________________________________
TABLE 7 ______________________________________ Fourth Embodiment dO
= 83.70761 .beta. = 1/5 NA = 0.57 Bf = 21.09296 L = 1100 r d n 1
1185.70800 19.00074 1.61298 2 477.18400 6.60188 3 1060.88800
30.01023 1.61536 4 -338.64042 1.12825 5 200.00000 32.71424 1.61536
6 -2276.77900 1.25667 7 248.82758 26.27974 1.61536 8 -1078.61200
3.19741 9 -726.49629 15.60000 1.61298 10 110.53957 25.83515 11
2000.00000 19.48735 1.48734 12 -236.03800 3.28431 13 -3000.00000
16.35209 1.61536 14 109.86653 32.21675 15 -153.78948 12.94478
1.61536 16 226.94451 35.22505 17 -132.31662 12.89677 1.61536 18
-830.43817 15.00000 19 -330.52996 22.58245 1.61536 20 -184.59786
0.39125 21 -1874.03800 28.55306 1.61536 22 -221.73570 0.72991 23
558.10318 33.51075 1.61536 24 -552.83568 0.96043 25 478.84376
25.74084 1.48734 26 -906.26315 0.33363 27 287.03514 23.69782
1.48734 28 2359.17900 0.83738 29 201.46068 26.38775 1.48734 30
155.19710 46.91024 31 198.66962 27.76454 1.61536 32 122.40099
26.77778 33 -220.19752 13.01538 1.61298 34 3835.74700 12.87579 35
-180.57897 13.15020 1.61298 36 270.91501 0.55149 37 250.92650
15.66663 1.48734 38 702.02997 25.47244 39 -1387.52600 15.36200
1.61298 40 404.60733 0.73901 41 437.56855 27.62162 1.48734 42
-242.82524 0.51051 43 476.89455 34.23933 1.48734 44 -364.55546
0.49298 45 500.11721 34.15684 1.61536 46 -381.64661 9.55181 47
-243.22857 18.84686 1.61298 48 -378.77918 0.50392 49 355.95061
30.00332 1.61536 50 6474.81200 0.49017 51 171.50098 30.27184
1.48734 52 722.00626 0.48766 53 113.44841 38.20547 1.48734 54
442.83450 3.61782 55 730.67537 19.05217 1.61298 56 73.59136
17.17240 57 78.92998 30.61882 1.48734 58 -315.11137 2.16189 59
-286.11801 26.15191 1.61536 60 -878.71576 (Bf)
______________________________________
TABLE 8 ______________________________________ Correspondent Values
to the Conditions for Fourth Embodiment (1) f1 /L = 0.119 (2) f2 /L
= -0.0278 (3) f3 /L = 0.106 (4) f4 /L = -0.0675 (5) f5 /L = 0.0805
(6) f6 /L = 0.146 (7) I/L = 2.29 (8) f4A/f4B = 1.94 (9) (r2Ff -
r2Fr) / (r2Ff + r2Fr) = 1.36 (10) (r4N - r4P) / (r4N + r4P) =
0.0383 (11) .vertline.r4N/L.vertline. = 0.246 (12)
.vertline.r4P/L.vertline. = 0.228 (13) f22/f23 = 1.17 (14) (r5p -
r5n) / (r5p + r5n) = 0.222 (15) (r5R - r6F) / (r5R + r6F) = -0.0350
(16) d56/L = 0.0156 (17) d6 /r6F = 1.01 (18) (r5F - r5R) / (r5F +
r5R) = 0.817 (19) f21/L = 0.395 (20) f2F/f2R = 0.603
______________________________________
Letting L be the distance (object-to-image distance) from the
object plane P1 (reticle plane) to the image plane P2 (wafer plane)
and .PHI. be a refractive power of lens surface in the sixth lens
group G.sub.6, in the first embodiment as described previously,
1/.vertline..PHI.L.vertline.=0.130 for the object-side lens surface
of the positive lens L.sub.61 and
1/.vertline..PHI.L.vertline.=0.532 for the object-side lens surface
of the negative lens L.sub.62, thus satisfying the condition (21).
In the second embodiment, 1/.vertline..PHI.L.vertline.=0.130 for
the object-side lens surface of the positive lens L.sub.61 and
1/.vertline..PHI.L.vertline.=0.550 for the object-side lens surface
of the negative lens L.sub.62, thus satisfying the condition (21).
In the third embodiment, 1/.vertline..PHI.L.vertline.=0.151 for the
object-side lens surface of the positive lens L.sub.61 and
1/.vertline..PHI.L.vertline.=0.468 for the object-side lens surface
of the negative lens L.sub.62, thus satisfying the condition (21).
In the fourth embodiment, 1/.vertline..PHI.L.vertline.=0.147 for
the object-side lens surface of the positive lens L.sub.61 and
1/.vertline..PHI.L.vertline.=0.423 for the object-side lens surface
of the negative lens L.sub.62, thus satisfying the condition
(21).
As described above, the sixth lens group G.sub.6 in each embodiment
is composed of three or less lenses including the lens surfaces
satisfying the condition (21).
It is understood from the above values of specifications for the
respective embodiments that the projection optical systems
according to the embodiments achieved satisfactory telecentricity
on the object side (reticle R side) and on the image side (wafer W
side) as securing the large numerical apertures and wide exposure
areas.
FIG. 7 to FIG. 22 are respectively aberration diagrams to show
aberrations in the first to fourth embodiments. Each of FIGS. 7,
11, 15, and 19 shows a spherical aberration of each embodiment.
Each of FIGS. 8, 12, 16, and 20 shows an astigmatism of each
embodiment. Each of FIGS. 9, 13, 17, and 21 shows a distortion of
each embodiment. Each of FIGS. 10, 14, 18, and 22 shows a coma of
each embodiment.
Here, in each aberration diagram, NA represents the numerical
aperture of the projection optical system 1, and Y the image
height, and in each astigmatism diagram, the dashed line represents
the meridional image surface and the solid line the sagittal image
surface.
It is understood from comparison of the aberration diagrams that
the aberrations are corrected in a good balance in each embodiment
even with a wide exposure area (image height) and a large numerical
aperture, particularly, distortion is extremely well corrected up
to nearly zero throughout the entire image, thus achieving the
projection optical system with high resolving power in a wide
exposure area.
The above-described embodiments showed the examples using the
mercury lamp as a light source for supplying the exposure light of
the i-line (365 nm), but it is needless to mention that the
invention is not limited to the examples; for example, the
invention may employ light sources including a mercury lamp
supplying the exposure light of the g-line (435 nm), and extreme
ultraviolet light sources such as excimer lasers supplying light of
193 nm or 248 nm.
In the above each embodiment the lenses constituting the projection
optical system are not cemented to each other, which can avoid a
problem of a change of cemented surfaces with time. Although in the
above each embodiment the lenses constituting the projection
optical system are made of a plurality of optic materials, they may
be made of a single glass material, for example quartz (SiO.sub.2)
if the wavelength region of the light source is not a wide
band.
As described above, the projection optical system according to the
present invention can achieve the bitelecentricity in a compact
design as securing a wide exposure area and a large numerical
aperture, and the invention can achieve the projection optical
system with high resolving power corrected in a good balance for
aberrations, particularly extremely well corrected for
distortion.
From the invention thus described, it will be obvious that the
invention may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims. The basic Japanese Application No. 872/1995 filed
on Jan. 6, 1995 is hereby incorporated by reference.
* * * * *